The present invention is a bioelectrical stimulus cable that is more biocompatible and has a greater number of leads than currently available bioelectrical stimulus cables.
Bioelectrical stimulus implant cables include cardiac implant cables, neuro-stimulus cables and any cable designed to apply an electric charge to body tissue or to supply a device which applies such a charge.
Bioelectrical stimulus cables must meet a number of challenging criteria. For example, a cardiac implant cable typically stretches from a subcutaneous fat deposit through the rib cage to a cardiac implant such as a pacemaker. The cable is continuously perturbed by the beating of the heart. It must not, however, become fatigued by this constant flexure to the point where a substantial number of the cable fibrils break. (A fibril is a thin wire used in a cable.) Not only does a broken fibril not conduct electricity to the implant but it also may work its way through the insulating layers of the cable and make harmful contact with body tissue. A bioelectrical stimulus cable must also be completely biocompatible. That is, the exterior of the cable must be made of biocompatible materials and the constant flexure caused by movement of the patient or his organs must not cause a rupture that would lead to the release of materials that are not biocompatible.
Heretofore, the general approach to the production of this type of cable has been to produce a tight helix so each fibril would experience only a small part of the total cable flexure. One problem with a tight helix is that it places a restriction on the number of independent leads that can be included in the cable. If more leads could be included in a cable, however, more purposes could be served with respect to an implant. For example, a single cardiac implant may function as both a pacemaker and as a defibrillator and may require a set of leads to power the pacemaker and a separate set of leads to power the defibrillator when it is needed. Additionally, a set of control leads may be necessary to, for example, adjust the operation of the pacemaker and the defibrillator.
Another problem encountered in the use of bioelectrical stimulus cables is the formation of scar tissue about the cable. It is occasionally necessary to replace a bioelectrical stimulus cable. Removing the old cable can provide a difficult challenge to the surgeon performing the replacement if considerable scar tissue has grown about and adhered itself to the cable, as is typical.
In a first preferred aspect the present invention is a high tensile strength bioelectrical stimulus cable comprising a conductor-insulator portion including conductive wires set into an insulating medium and a braided sheath encompassing the conductor-insulator portion and defining an inner diameter, the inner diameter shrinking when the cable is pulled longitudinally, thereby squeezing the conductor-insulator portion and increasing the tensile strength of the cable.
In a second separate preferred aspect, the present invention is a bioelectrical stimulus cable comprising at least one insulated electrical lead, the insulated electrical lead including at least one fibril, a coating of rigid, insulating, low friction material tightly set about the fibril and a coating of shock dampening elastomeric, insulating material tightly set about the rigid, insulating, low friction material.
In a third separate preferred aspect the present invention is a bioelectrical stimulus cable comprising a conductor-insulator portion including conductive wires set into an insulating medium and an outer layer having a low friction outer surface.
In a fourth separate preferred aspect the present invention is a cardiac implant cable comprising a set of more than six insulated leads, wrapped in a helix having a lay length of greater than 10 mm (0.4xe2x80x3).
In a fifth separate preferred aspect the present invention is a bioelectrical stimulus cable comprising a conductor-insulator portion including conductive wires set into an insulating medium and an outer layer having an outer surface textured with holes of between 2 microns and 150 microns in diameter and thereby adapted to promote the growth of neovascularized tissue.
In a sixth separate preferred aspect the present invention is a bioelectrical stimulus cable that comprises a set of fibrils, each of which has a diameter of less than 30 xcexcm and which are configured together longitudinally. The set of fibrils is electrically isolated by insulative material.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.